class Net::LDAP::Filter

def join(left, right)

z = Net::LDAP::Filter.join(x, y)
# Selects only entries that meet both conditions above.
y = Net::LDAP::Filter.eq("mail", "George*")
# with "George".
# Selects only entries that have a mail attribute that begins
x = Net::LDAP::Filter.present("objectclass")
# Selects only entries that have an objectclass attribute.

right.
Filter.join(left, right) is the same as left &
Joins two or more filters so that all conditions must be true. Calling
# 
def join(left, right)
  new(:and, left, right)
end